Field of the Invention
The present invention relates to a drive device, and more particularly to a rotation drive device.
Related Prior Art
With the maturation of automation, automatic machines must employ various drive devices to perform different automatic operations, and most of the drive devices are generally categorized into devices of linear motion and rotation motion. As shown in FIG. 1, inside an articulated robot arm 10 is provided a drive source 11 which dynamically connected to a crankshaft 12, and the crankshaft 12 drives a driven device 13 to rotate.
The crankshaft 12 includes a driven portion 123, a shaft portion 122 and a drive portion 121 which are sequentially connected to one another. The drive portion 121 has a diameter smaller than the driven portion 123, and the drive portion 121 and the driven portion 123 are concentrically arranged. The shaft portion 122 has two ends connected to the drive and driven portions 121, 123 at the same central angle of a circle. The same central angle refers to the positions of the two ends of the shaft portion 122, under the condition that the drive portion 121 and the driven portion 123 are concentric with each other.
Since the two ends of the shaft portion 122 are located at the same central angle, namely, the shaft portion 122 extends along the outmost periphery of a space between the drive and driven portions 121, 123, wires can only be allocated at one side of the shaft portion 122, that will adversely affect the rotation angle of the driven device 13, and increase the wear ratio of the wire. Besides, the wiring space of the existing hollow gear reducer is limited by the diameter of the hollow shaft. A large-diameter hollow shaft may provide a bigger wiring space but will increase the size and cost of the robot arm, and will also unfavorably affect the flexibility of the robot arm.
The present invention has arisen to mitigate and/or obviate the afore-described disadvantages.